Organic electroluminescent compound and organic electroluminescent device comprising the same

ABSTRACT

The present disclosure relates to an organic electroluminescent compound and an organic electroluminescent device comprising the same. The organic electroluminescent compound of the present disclosure provides an organic electroluminescent device having high efficiency and/or long lifespan.

TECHNICAL FIELD

The present disclosure relates to an organic electroluminescent compoundand an organic electroluminescent device comprising the same.

BACKGROUND ART

An electroluminescent (EL) device is a self-light-emitting device withthe advantages of providing a wider viewing angle, a greater contrastratio, and a faster response time. The first organic EL device wasdeveloped by Eastman Kodak, by using small aromatic diamine moleculesand aluminum complexes as materials for forming a light-emitting layer(see Appl. Phys. Lett. 51, 913, 1987).

An organic EL device changes electric energy into light by the injectionof a charge into an organic light-emitting material, and commonlycomprises an anode, a cathode, and an organic layer formed between thetwo electrodes. The organic layer of the organic EL device may becomposed of a hole injection layer, a hole transport layer, an electronblocking layer, a light-emitting layer (containing host and dopantmaterials), an electron buffer layer, a hole blocking layer, an electrontransport layer, an electron injection layer, etc.; the materials usedin the organic layer can be classified into a hole injection material, ahole transport material, an electron blocking material, a light-emittingmaterial, an electron buffer material, a hole blocking material, anelectron transport material, an electron injection material, etc.,depending on functions. In the organic EL device, holes from an anodeand electrons from a cathode are injected into a light-emitting layer byelectric voltage, and an exciton having high energy is produced by therecombination of the holes and electrons. The organic light-emittingcompound moves into an excited state by the energy and emits light fromenergy when the organic light-emitting compound returns to the groundstate from the excited state.

The most important factor determining luminous efficiency in an organicEL device is light-emitting materials. The light-emitting materials arerequired to have the following features: high quantum efficiency, highmovement degree of an electron and a hole, and uniformity and stabilityof the formed light-emitting material layer. The light-emitting materialis classified into blue, green, and red light-emitting materialsaccording to the light-emitting color, and further includes yellow ororange light-emitting materials. Furthermore, the light-emittingmaterial is classified into a host material and a dopant material in afunctional aspect. Recently, an urgent task is the development of anorganic EL device having high efficiency and/or long lifespan. Inparticular, the development of highly excellent light-emitting materialover conventional materials is urgently required, considering the ELproperties necessary for medium- and large-sized OLED panels. For this,preferably, as a solvent in a solid state and an energy transmitter, ahost material should have high purity and a suitable molecular weight inorder to be deposited under vacuum. Furthermore, a host material isrequired to have high glass transition temperature and pyrolysistemperature for guaranteeing thermal stability, high electrochemicalstability for long lifespan, easy formability of an amorphous thin film,good adhesion with adjacent layers, and no movement between layers.

Further, the electron buffer layer is equipped to improve a problem oflight-emitting luminance reduction which may occur due to the change ofcurrent properties in the device when the device is exposed to a hightemperature during a process of producing panels. Thus, the propertiesof the compounds comprised in the electron buffer layer are important.In addition, the compound used for the electron buffer layer performs arole of controlling an electron injection by the electron withdrawingcharacteristics and the electron affinity LUMO (lowest unoccupiedmolecular orbital) energy level, and thus performs a role to improve theefficiency and lifespan of the organic electroluminescent device.

Meanwhile, in an organic EL device, an electron transport materialactively transports electrons from a cathode to a light-emitting layerand inhibits transport of holes which are not recombined in thelight-emitting layer to increase recombination opportunity of holes andelectrons in the light-emitting layer. Thus, electron-affinitivematerials are used as an electron transport material. Organic metalcomplexes having light-emitting function such as Alq₃ are excellent intransporting electrons, and thus have been conventionally used as anelectron transport material. However, Alq₃ has problems in that it movesto other layers and shows reduction of color purity when used in bluelight-emitting devices. Therefore, new electron transport materials havebeen required, which do not have the above problems, are highlyelectron-affinitive, and quickly transport electrons in organic ELdevices to provide organic EL devices having high luminous efficiency.

Korean Patent No. 1297158 discloses a compound wherein a heteroaryl isbonded to a carbon position other than a naphthalene ring in anaphthoxazole structure via an arylene as a linker; Korean Patent Appln.Laying-Open No. KR 2008-0028424 A discloses a naphthoimidazolederivative; European Patent Application Publication No. EP 1593675 A1discloses a compound wherein an amine is bonded to a carbon position ofa benzene ring, which is directly fused with an oxazole in anaphthoxazole structure, via arylene as a linker; and Korean Patent No.1202349 discloses a benzoindene derivative. However, the abovereferences fail to disclose a compound wherein a heteroaryl is bonded toa carbon position of a benzene ring, which is not directly fused with anoxazole in a naphthoxazole structure, directly or via an arylene as alinker.

In addition, Korean Patent Appln. Laying-Open No. KR 2015-0136033 Adiscloses a compound wherein a heteroaryl is bonded to a carbon positionof a benzene ring, which is not directly fused with an oxazole in anaphthoxazole structure, directly or via an arylene as a linker.However, the compound disclosed in KR 2015-0136033 A is different fromthe compound of the present disclosure in the position of thesubstituents.

DISCLOSURE OF THE INVENTION Problems to be Solved

The objective of the present disclosure is to provide an organicelectroluminescent compound effective to produce an organicelectroluminescent device having relatively low driving voltage and/orexcellent luminous efficiency.

Solution to Problems

The present inventors found that the above objective can be achieved byan organic electroluminescent compound represented by the followingformula 1:

wherein

X₁ and X₂ each independently represent N, O, or S, with the proviso,when X₁ represents N, X₂ represents O or S, and when X₁ represents O orS, X₂ represents N;

Z₁ and Z₂ each independently represent hydrogen, deuterium, or -L₁-Het,with the proviso, at least one of Z₁ and Z₂ represents -L₁-Het;

R represents a substituted or unsubstituted (C6-C30)aryl, or asubstituted or unsubstituted 3- to 30-membered heteroaryl;

R₁ to R₄ each independently represent hydrogen, deuterium, a substitutedor unsubstituted (C1-C10)alkyl, a substituted or unsubstituted(C6-C30)aryl, or a substituted or unsubstituted 3- to 30-memberedheteroaryl;

L₁ represents a direct bond, a substituted or unsubstituted(C6-C30)arylene, or a substituted or unsubstituted 3- to 30-memberedheteroarylene;

Het represents a substituted or unsubstituted 3- to 30-memberedheteroaryl; and

the heteroaryl(ene) contains at least one heteroatom selected from B, N,O, S, Si, and P.

Effects of the Invention

By using the organic electroluminescent compound according to thepresent disclosure, an organic EL device with relatively low drivingvoltage and/or excellent luminous efficiency is provided. The organicelectroluminescent compound according to the present disclosure may beused as an electron buffer material to provide an organic EL device withexcellent driving voltage and/or luminous efficiency characteristics,and it may be used as an electron transport material to provideexcellent effects in driving voltage, luminous efficiency, and/or in anaspect of color coordinates of a device. In addition, the organicelectroluminescent compound according to the present disclosure may alsobe used as a phosphorescent host.

EMBODIMENTS OF THE INVENTION

Hereinafter, the present disclosure will be described in detail.However, the following description is intended to explain the invention,and is not meant in any way to restrict the scope of the invention.

The term “organic electroluminescent compound” in the present disclosuremeans a compound that may be used in an organic electroluminescentdevice, and may be comprised in any layer constituting an organicelectroluminescent device, as necessary.

The term “organic electroluminescent material” in the present disclosuremeans a material that may be used in an organic electroluminescentdevice, and may comprise at least one compound. The organicelectroluminescent material may be comprised in any layer constitutingan organic electroluminescent device, as necessary. For example, theorganic electroluminescent material may be a hole injection material, ahole transport material, a hole auxiliary material, a light-emittingauxiliary material, an electron blocking material, a light-emittingmaterial, an electron buffer material, a hole blocking material, anelectron transport material, or an electron injection material.

The organic electroluminescent material of the present disclosure maycomprise at least one compound represented by formula 1. The compoundrepresented by formula 1 may be comprised in at least one layerconstituting an organic electroluminescent device, and may be comprisedin an electron buffer layer as an electron buffer material and/or anelectron transport layer as an electron transport material, but is notlimited thereto.

Hereinafter, the organic electroluminescent compound represented byformula 1 will be described in detail.

Herein, “(C1-C30)alkyl” is meant to be a linear or branched alkyl having1 to 30 carbon atoms constituting the chain, in which the number ofcarbon atoms is preferably 1 to 10, more preferably 1 to 6, and includesmethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, etc.“(C2-C30)alkenyl” is meant to be a linear or branched alkenyl having 2to 30 carbon atoms constituting the chain, in which the number of carbonatoms is preferably 2 to 20, more preferably 2 to 10, and includesvinyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl,2-methylbut-2-enyl, etc. “(C2-C30)alkynyl” is a linear or branchedalkynyl having 2 to 30 carbon atoms constituting the chain, in which thenumber of carbon atoms is preferably 2 to 20, more preferably 2 to 10,and includes ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl,3-butynyl, 1-methylpent-2-ynyl, etc. “(C3-C30)cycloalkyl” is a mono- orpolycyclic hydrocarbon having 3 to 30 ring backbone carbon atoms, inwhich the number of carbon atoms is preferably 3 to 20, more preferably3 to 7, and includes cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,etc. “3- to 7-membered heterocycloalkyl” is a cycloalkyl having at leastone heteroatom selected from the group consisting of B, N, O, S, Si, andP, preferably O, S, and N, and 3 to 7 ring backbone atoms, and includestetrahydrofuran, pyrrolidine, thiolan, tetrahydropyran, etc.“(C6-C30)aryl(ene)” is a monocyclic or fused ring derived from anaromatic hydrocarbon having 6 to 30 ring backbone carbon atoms, in whichthe number of ring backbone carbon atoms is preferably 6 to 20, morepreferably 6 to 15, and includes phenyl, biphenyl, terphenyl, naphthyl,binaphthyl, phenylnaphthyl, naphthylphenyl, fluorenyl, phenylfluorenyl,benzofluorenyl, dibenzofluorenyl, phenanthrenyl, phenylphenanthrenyl,anthracenyl, indenyl, triphenylenyl, pyrenyl, tetracenyl, perylenyl,chrysenyl, naphthacenyl, fluoranthenyl, etc. “3- to 30-memberedheteroaryl(ene)” is an aryl group having at least one, preferably 1 to 4heteroatoms selected from the group consisting of B, N, O, S, Si, and P,and 3 to 30 ring backbone atoms, in which the number of ring backboneatoms is preferably 3 to 20, more preferably 5 to 15; is a monocyclicring, or a fused ring condensed with at least one benzene ring; may bepartially saturated; may be one formed by linking at least oneheteroaryl or aryl group to a heteroaryl group via a single bond(s); andincludes a monocyclic ring-type heteroaryl including furyl, thiophenyl,pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl,isoxazolyl, oxazolyl, oxadiazolyl, triazinyl, tetrazinyl, triazolyl,tetrazolyl, furazanyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl,etc., and a fused ring-type heteroaryl including benzofuranyl,benzothiophenyl, isobenzofuranyl, dibenzofuranyl, dibenzothiophenyl,benzonaphthothiophenyl, benzimidazolyl, benzothiazolyl,benzoisothiazolyl, benzoisoxazolyl, benzoxazolyl, isoindolyl, indolyl,indazolyl, benzothiadiazolyl, quinolyl, isoquinolyl, cinnolinyl,quinazolinyl, quinoxalinyl, carbazolyl, phenoxazinyl, phenanthridinyl,benzodioxolyl, etc. “Halogen” includes F, Cl, Br, and I.

The compound of formula 1 may be represented by the following formula 2or 3:

wherein X₁, X₂, Z₁, Z₂, R, and R₁ to R₄ are as defined in formula 1.

Also, the compound of formula 2 or 3 may be represented by any one ofthe following formulae 4 to 7:

wherein X₁, X₂, Z₁, Z₂, and R are as defined in formula 1.

Herein, “substituted” in the expression “substituted or unsubstituted”means that a hydrogen atom in a certain functional group is replacedwith another atom or functional group, i.e., a substituent. Thesubstituents of the substituted alkyl, the substituted aryl(ene), andthe substituted heteroaryl(ene) in R, R₁ to R₄, L₁, and Het in formula 1each independently are at least one selected from the group consistingof deuterium, a halogen, a cyano, a carboxyl, a nitro, a hydroxyl, a(C1-C30)alkyl, a halo(C1-C30)alkyl, a (C2-C30)alkenyl, a(C2-C30)alkynyl, a (C1-C30)alkoxy, a (C1-C30)alkylthio, a(C3-C30)cycloalkyl, a (C3-C30)cycloalkenyl, a 3- to 7-memberedheterocycloalkyl, a (C6-C30)aryloxy, a (C6-C30)arylthio, a 3- to30-membered heteroaryl unsubstituted or substituted with a (C6-C30)aryl,a (C6-C30)aryl unsubstituted or substituted with a 3- to 30-memberedheteroaryl, a tri(C1-C30)alkylsilyl, a tri(C6-C30)arylsilyl, adi(C1-C30)alkyl(C6-C30)arylsilyl, a (C1-C30)alkyldi(C6-C30)arylsilyl, anamino, a mono- or di-(C1-C30)alkylamino, a mono- ordi-(C6-C30)arylamino, a (C1-C30)alkyl(C6-C30)arylamino, a(C1-C30)alkylcarbonyl, a (C1-C30)alkoxycarbonyl, a (C6-C30)arylcarbonyl,a di(C6-C30)arylboronyl, a di(C1-C30)alkylboronyl, a(C1-C30)alkyl(C6-C30)arylboronyl, a (C6-C30)aryl(C1-C30)alkyl, and a(C1-C30)alkyl(C6-C30)aryl; and preferably each independently are a(C1-C6)alkyl or a (C6-C12)aryl.

In formula 1, X₁ and X₂ each independently represent N, O, or S, withthe proviso, when X₁ represents N, X₂ represents O or S, and when X₁represents O or S, X₂ represents N.

Z₁ and Z₂ each independently represent hydrogen, deuterium, or -L₁-Het,with the proviso, at least one of Z₁ and Z₂ represents -L₁-Het.

R represents a substituted or unsubstituted (C6-C30)aryl, or asubstituted or unsubstituted 3- to 30-membered heteroaryl; preferablyrepresents a substituted or unsubstituted (C6-C18)aryl, or a substitutedor unsubstituted 5- to 18-membered heteroaryl; and more preferablyrepresents an unsubstituted (C6-C18)aryl, or an unsubstituted 5- to18-membered heteroaryl.

R₁ to R₄ each independently represent hydrogen, deuterium, a substitutedor unsubstituted (C1-C10)alkyl, a substituted or unsubstituted(C6-C30)aryl, or a substituted or unsubstituted 3- to 30-memberedheteroaryl; and preferably each independently represent hydrogen.

L₁ represents a direct bond, a substituted or unsubstituted(C6-C30)arylene, or a substituted or unsubstituted 3- to 30-memberedheteroarylene; preferably represents a direct bond, a substituted orunsubstituted (C6-C18)arylene, or a substituted or unsubstituted 5- to18-membered heteroarylene; and more preferably represents a direct bond,a (C6-C18)arylene unsubstituted or substituted with a (C1-C6)alkyl, oran unsubstituted 5- to 18-membered heteroarylene.

Het represents a substituted or unsubstituted 3- to 30-memberedheteroaryl; preferably represents a substituted or unsubstituted 5- to18-membered heteroaryl; and more preferably represents a 5- to18-membered heteroaryl unsubstituted or substituted with a (C6-C12)aryl.

Specifically, Het may be a substituted or unsubstituted pyridine, asubstituted or unsubstituted pyrimidine, a substituted or unsubstitutedtriazine, a substituted or unsubstituted quinoline, a substituted orunsubstituted isoquinoline, a substituted or unsubstituted quinazoline,a substituted or unsubstituted quinoxaline, a substituted orunsubstituted triazole, a substituted or unsubstituted pyrazole, asubstituted or unsubstituted benzofuran, a substituted or unsubstituteddibenzofuran, a substituted or unsubstituted benzothiophene, or asubstituted or unsubstituted dibenzothiophene.

According to one embodiment of the present disclosure, in formula 1, X₁and X₂ each independently represent N, O, or S, with the proviso, whenX₁ represents N, X₂ represents O or S, and when X₁ represents O or S, X₂represents N; Z₁ and Z₂ each independently represent hydrogen or-L₁-Het, with the proviso, at least one of Z₁ and Z₂ represents -L₁-Het;R represents a substituted or unsubstituted (C6-C18)aryl, or asubstituted or unsubstituted 5- to 18-membered heteroaryl; R₁ to R₄ eachindependently represent hydrogen; L₁ represents a direct bond, asubstituted or unsubstituted (C6-C18)arylene, or a substituted orunsubstituted 5- to 18-membered heteroarylene; and Het represents asubstituted or unsubstituted 5- to 18-membered heteroaryl.

According to another embodiment of the present disclosure, in formula 1,X₁ and X₂ each independently represent N, O, or S, with the proviso,when X₁ represents N, X₂ represents O or S, and when X₁ represents O orS, X₂ represents N; Z₁ and Z₂ each independently represent hydrogen or-L₁-Het, with the proviso, at least one of Z₁ and Z₂ represents -L₁-Het;R represents an unsubstituted (C6-C18)aryl, or an unsubstituted 5- to18-membered heteroaryl; R₁ to R₄ each independently represent hydrogen;L₁ represents a direct bond, a (C6-C18)arylene unsubstituted orsubstituted with a (C1-C6)alkyl, or an unsubstituted 5- to 18-memberedheteroarylene; and Het represents a 5- to 18-membered heteroarylunsubstituted or substituted with a (C6-C12)aryl.

The organic electroluminescent compound represented by formula 1 may beselected from the group consisting of the following compounds, but isnot limited thereto:

The organic electroluminescent compound according to the presentdisclosure can be prepared by known methods to one skilled in the art,and can be prepared, for example, according to the following reactionscheme:

wherein

X₁, X₂, R, L₁, and Het are as defined in formula 1, and Hal represents ahalogen.

The present disclosure provides an organic electroluminescent materialcomprising the organic electroluminescent compound of formula 1, and anorganic EL device comprising the material.

The material can be comprised of the organic electroluminescent compoundof the present disclosure alone, or can be a mixture or composition foran organic electroluminescent material which further comprisesconventional materials generally included in organic electroluminescentmaterials.

The organic electroluminescent device according to the presentdisclosure may comprise a first electrode, a second electrode, and atleast one organic layer between the first and second electrodes. Theorganic layer may comprise at least one organic electroluminescentcompound of formula 1.

One of the first and second electrodes may be an anode, and the othermay be a cathode. The organic layer may comprise a light-emitting layer,and may further comprise at least one layer selected from a holeinjection layer, a hole transport layer, a hole auxiliary layer, alight-emitting auxiliary layer, an electron transport layer, an electronbuffer layer, an electron injection layer, an interlayer, a holeblocking layer, and an electron blocking layer.

The organic electroluminescent compound of formula 1 may be comprised inat least one layer of the light-emitting layer, the hole injectionlayer, the hole transport layer, the hole auxiliary layer, thelight-emitting auxiliary layer, the electron transport layer, theelectron buffer layer, the electron injection layer, the interlayer, thehole blocking layer, and the electron blocking layer, preferably in atleast one layer of the light-emitting layer, the electron buffer layer,and the electron transport layer. When used in the light-emitting layer,the organic electroluminescent compound of formula 1 may be comprised asa phosphorescent host material; when used in the electron buffer layer,the organic electroluminescent compound of formula 1 may be comprised asan electron buffer material; and when used in the electron transportlayer, the organic electroluminescent compound of formula 1 may becomprised as an electron transport material.

The light-emitting layer may comprise at least one host and at least onedopant. The light-emitting layer emits light, which may be a singlelayer or multi-layers having two or more layers. The dopingconcentration of the dopant compound to the host compound in thelight-emitting layer is preferably less than 20 wt %.

Preferably, the light-emitting layer may comprise at least one dopant,and, if necessary, may further comprise another compound besides theorganic electroluminescent compound of formula 1 as a host material.When the organic electroluminescent compound of formula 1 is comprisedas a host material, the weight ratio of the compound of formula 1 (firsthost material) to the other compound besides the compound of formula 1(second host material) is in the range of 1:99 to 99:1.

The host material consisting of another compound besides the compound offormula 1 can be used of any of the known hosts. In terms of luminousefficiency, the host material consisting of another compound besides thecompound of formula 1 may be preferably selected from the groupconsisting of the compounds represented by the following formulae 11 to16:

wherein

Cz represents the following structure:

A represents —O— or —S—; and

R₂₁ to R₂₄, each independently, represent hydrogen, deuterium, ahalogen, a substituted or unsubstituted (C1-C30)alkyl, a substituted orunsubstituted (C6-C30)aryl, a substituted or unsubstituted (5- to30-membered)heteroaryl, or —SiR₂₅R₂₆R₂₇; in which R₂₅ to R₂₇, eachindependently, represent a substituted or unsubstituted (C1-C30)alkyl,or a substituted or unsubstituted (C6-C30)aryl; L₄ represents a singlebond, a substituted or unsubstituted (C6-C30)arylene, or a substitutedor unsubstituted (5- to 30-membered)heteroarylene; M represents asubstituted or unsubstituted (C6-C30)aryl, or a substituted orunsubstituted (5- to 30-membered)heteroaryl; Y₁ and Y₂, eachindependently, represent —O—, —S—, —NR₃₁— or —CR₃₂R₃₃—, with the provisothat Y₁ and Y₂ are not present simultaneously; R₃₁ to R₃₃, eachindependently, represent a substituted or unsubstituted (C1-C30)alkyl, asubstituted or unsubstituted (C6-C30)aryl, or a substituted orunsubstituted (5- to 30-membered)heteroaryl; R₃₂ and R₃₃ may be the sameor different; h and i, each independently, represent an integer of 1 to3; j, k, l, and m, each independently, represent an integer of 0 to 4;where if h, i, j, k, l, or m represents an integer of 2 or more, each(Cz-La), each (Cz), each R₂₁, each R₂₂, each R₂₃, or each R₂₄ may be thesame or different;

wherein

Y₃ to Y₅, each independently, represent CR₃₄ or N, in which R₃₄represents hydrogen, a substituted or unsubstituted (C1-C30)alkyl, asubstituted or unsubstituted (C6-C30)aryl, or a substituted orunsubstituted (5- to 30-membered)heteroaryl;

B₁ and B₂, each independently, represent hydrogen, a substituted orunsubstituted (C6-C30)aryl, or a substituted or unsubstituted (5- to30-membered)heteroaryl;

B₃ represents a substituted or unsubstituted (C6-C30)aryl, or asubstituted or unsubstituted (5- to 30-membered)heteroaryl; and

L₅ represents a single bond, a substituted or unsubstituted(C6-C30)arylene, or a substituted or unsubstituted (5- to30-membered)heteroarylene.

Specifically, the preferred examples of the second host material are asfollows, but are not limited thereto.

[wherein, TPS represents a triphenylsilyl group.]

When the compound of the present disclosure is used as a host, one ormore phosphorescent dopants may be preferably used as a dopant. Thephosphorescent dopant material is not particularly limited, but may bepreferably selected from the metallated complex compounds of iridium(Ir), osmium (Os), copper (Cu), and platinum (Pt), more preferablyselected from ortho-metallated complex compounds of iridium (Ir), osmium(Os), copper (Cu), and platinum (Pt), and even more preferablyortho-metallated iridium complex compounds.

The dopant may comprise a compound selected from the group consisting ofthe compounds represented by the following formulae 101 to 104, but isnot limited thereto.

wherein, L is selected from the following structures:

R₁₀₀, R₁₃₄, and R₁₃₅, each independently, represent hydrogen, deuterium,a substituted or unsubstituted (C1-C30)alkyl, or a substituted orunsubstituted (C3-C30)cycloalkyl;

R₁₀₁ to R₁₀₉ and R₁₁₁ to R₁₂₃, each independently, represent hydrogen,deuterium, a halogen, a (C1-C30)alkyl unsubstituted or substituted witha halogen, a substituted or unsubstituted (C3-C30)cycloalkyl, asubstituted or unsubstituted (C6-C30)aryl, a cyano, or a substituted orunsubstituted (C1-C30)alkoxy; adjacent substituents of R₁₀₆ to R₁₀₉ maybe linked to each other to form a substituted or unsubstituted fusedring, e.g., a fluorene unsubstituted or substituted with an alkyl, adibenzothiophene unsubstituted or substituted with an alkyl, or adibenzofuran unsubstituted or substituted with an alkyl; and adjacentsubstituents of R₁₂₀ to R₁₂₃ may be linked to each other to form asubstituted or unsubstituted fused ring, e.g., a quinoline unsubstitutedor substituted with an alkyl or an aryl;

R₁₂₄ to R₁₃₃ and R₁₃₆ to R₁₃₉, each independently, represent hydrogen,deuterium, a halogen, a substituted or unsubstituted (C1-C30)alkyl, or asubstituted or unsubstituted (C6-C30)aryl; and adjacent substituents ofR₁₂₄ to R₁₂₇ may be linked to each other to form a substituted orunsubstituted fused ring, e.g., a fluorene unsubstituted or substitutedwith an alkyl, a dibenzothiophene unsubstituted or substituted with analkyl, or a dibenzofuran unsubstituted or substituted with an alkyl;

X represents CR₁₁R₁₂, O, or S;

R₁₁ and R₁₂, each independently, represent a substituted orunsubstituted (C1-C10)alkyl, or a substituted or unsubstituted(C6-C30)aryl;

R₂₀₁ to R₂₁₁, each independently, represent hydrogen, deuterium, ahalogen, a (C1-C30)alkyl unsubstituted or substituted with a halogen, asubstituted or unsubstituted (C3-C30)cycloalkyl, or a substituted orunsubstituted (C6-C30)aryl; and adjacent substituents of R₂₀₅ to R₂₁₁may be linked to each other to form a substituted or unsubstituted fusedring, e.g., a fluorene unsubstituted or substituted with an alkyl, adibenzothiophene unsubstituted or substituted with an alkyl, or adibenzofuran unsubstituted or substituted with an alkyl;

f and g, each independently, represent an integer of 1 to 3; where f org is an integer of 2 or more, each R₁₀₀ may be the same or different;and

n represents an integer of 1 to 3.

The specific examples of the dopant compound are as follows:

In addition, the present disclosure provides an electron transportmaterial or an electron buffer material comprising the organicelectroluminescent compound of formula 1.

The electron buffer material may control flow properties of a charge.For example, the electron buffer material may trap an electron, block anelectron, or lower an energy barrier between an electron transport zoneand a light-emitting layer. The electron buffer material in an organicelectroluminescent device may be used for an electron buffer layer, ormay be used in another zone such as an electron transport zone or alight-emitting layer, in which the electron buffer layer is formedbetween the light-emitting layer and the electron transport zone, orbetween the electron transport zone and the second electrode. Theelectron buffer material may further comprise conventional materialsgenerally used in producing an organic electroluminescent device.

When the organic electroluminescent compound of formula 1 is used as anelectron transport material, the electron transport material can becomprised of the organic electroluminescent compound of formula 1 alone,or can further comprise conventional materials generally included inelectron transport materials.

When the compound according to the present disclosure is used as anelectron transport material or an electron buffer material, alight-emitting layer comprised in the organic electroluminescent devicemay comprise a host and a dopant. The host compound may be aphosphorescent host compound or a fluorescent host compound, and thedopant compound may be a phosphorescent dopant compound or a fluorescentdopant compound. As the fluorescent host material, an anthracenederivative, an aluminum complex, a rubrene derivative, an arylaminederivative, etc., and preferably an anthracene derivative may be used.The specific examples of the fluorescent host material may be asfollows, but are not limited thereto:

In addition, as the fluorescent dopant material, derivatives of pyrenes,aminofluorenes, aminoanthracenes, aminochrysenes, stilbenes, etc., andpreferably pyrene derivatives may be used.

The specific examples of the fluorescent dopant material may be asfollows, but are not limited thereto:

The organic electroluminescent device of the present disclosure mayfurther comprise at least one compound selected from the groupconsisting of arylamine-based compounds and styrylarylamine-basedcompounds.

In the organic electroluminescent device of the present disclosure, theorganic layer may further comprise at least one metal selected from thegroup consisting of metals of Group 1, metals of Group 2, transitionmetals of the 4th period, transition metals of the 5th period,lanthanides, and organic metals of the d-transition elements of thePeriodic Table, or at least one complex compound comprising the metal.

In addition, the organic electroluminescent device of the presentdisclosure may emit white light by further comprising at least onelight-emitting layer, which comprises a blue, a red, or a greenelectroluminescent compound known in the field, besides the compound ofthe present disclosure. If necessary, it may further comprise a yellowor an orange light-emitting layer.

In the organic electroluminescent device of the present disclosure,preferably, at least one layer selected from a chalcogenide layer, ametal halide layer, and a metal oxide layer (hereinafter, “a surfacelayer”) may be placed on an inner surface(s) of one or bothelectrode(s). Specifically, a chalcogenide (includes oxides) layer ofsilicon or aluminum is preferably placed on an anode surface of anelectroluminescent medium layer, and a metal halide layer or a metaloxide layer is preferably placed on a cathode surface of anelectroluminescent medium layer. Such a surface layer provides operationstability for the organic electroluminescent device. Preferably, thechalcogenide includes SiO_(X)(1≤X≤2), AlO_(X)(1≤X≤1.5), SiON, SiAlON,etc.; the metal halide includes LiF, MgF₂, CaF₂, a rare earth metalfluoride, etc.; and the metal oxide includes Cs₂O, Li₂O, MgO, SrO, BaO,CaO, etc.

A hole injection layer, a hole transport layer, an electron blockinglayer, or a combination thereof can be used between the anode and thelight-emitting layer. The hole injection layer may be multi-layers inorder to lower the hole injection barrier (or hole injection voltage)from the anode to the hole transport layer or the electron blockinglayer, wherein each of the multi-layers may use two compoundssimultaneously. The hole transport layer or the electron blocking layermay also be multi-layers.

An electron buffer layer, a hole blocking layer, an electron transportlayer, an electron injection layer, or a combination thereof can be usedbetween the light-emitting layer and the cathode. The electron bufferlayer may be multi-layers in order to control the injection of theelectron and improve the interfacial properties between thelight-emitting layer and the electron injection layer, wherein each ofthe multi-layers may use two compounds simultaneously. The hole blockinglayer or the electron transport layer may also be multi-layers, whereineach of the multi-layers may use a multi-component of compounds.

The light-emitting auxiliary layer may be placed between the anode andthe light-emitting layer, or between the cathode and the light-emittinglayer. When the light-emitting auxiliary layer is placed between theanode and the light-emitting layer, it can be used for promoting thehole injection and/or hole transport, or for preventing the overflow ofelectrons. When the light-emitting auxiliary layer is placed between thecathode and the light-emitting layer, it can be used for promoting theelectron injection and/or electron transport, or for preventing theoverflow of holes. Also, the hole auxiliary layer may be placed betweenthe hole transport layer (or hole injection layer) and thelight-emitting layer, and may be effective to promote or block the holetransport rate (or hole injection rate), thereby enabling the chargebalance to be controlled. Further, the electron blocking layer may beplaced between the hole transport layer (or hole injection layer) andthe light-emitting layer, and can confine the excitons within thelight-emitting layer by blocking the overflow of electrons from thelight-emitting layer to prevent a light-emitting leakage. When anorganic electroluminescent device includes two or more hole transportlayers, the hole transport layer, which is further included, may be usedas a hole auxiliary layer or an electron blocking layer. The holeauxiliary layer and the electron blocking layer may have an effect ofimproving the efficiency and/or the lifespan of the organicelectroluminescent device.

Preferably, in the organic electroluminescent device of the presentdisclosure, a mixed region of an electron transport compound and areductive dopant, or a mixed region of a hole transport compound and anoxidative dopant may be placed on at least one surface of a pair ofelectrodes. In this case, the electron transport compound is reduced toan anion, and thus it becomes easier to inject and transport electronsfrom the mixed region to the light-emitting medium. Furthermore, thehole transport compound is oxidized to a cation, and thus it becomeseasier to inject and transport holes from the mixed region to thelight-emitting medium. Preferably, the oxidative dopant includes variousLewis acids and acceptor compounds; and the reductive dopant includesalkali metals, alkali metal compounds, alkaline earth metals, rare-earthmetals, and mixtures thereof. The reductive dopant layer may be employedas a charge-generating layer to prepare an organic EL device having twoor more light-emitting layers and emitting white light.

In order to form each layer constituting the organic EL device of thepresent disclosure, dry film-forming methods such as vacuum deposition,sputtering, plasma, ion plating methods, etc., or wet film-formingmethods such as spin coating, dip coating, flow coating methods, etc.,can be used. The first and second host compounds of the presentdisclosure may be co-evaporated or mixture-evaporated.

When using a wet film-forming method, a thin film is formed bydissolving or dispersing the material constituting each layer insuitable solvents, such as ethanol, chloroform, tetrahydrofuran,dioxane, etc. The solvents are not specifically limited as long as thematerial constituting each layer is soluble or dispersible in thesolvents, which do not cause any problems in forming a layer.

By using the organic electroluminescent device of the presentdisclosure, a display system, for example, for smartphones, tablets,notebooks, PCs, TVs, or vehicles, or a lighting system, for example, anindoor or outdoor lighting system, can be produced.

Hereinafter, the preparation method of the organic electroluminescentcompounds of the present disclosure, the physical properties of thecompounds, and the luminous properties of the organic electroluminescentdevice comprising the compounds will be explained in detail withreference to the representative compounds of the present disclosure.

Example 1: Preparation of Compound C-35

Preparation of Compound 1-1

22.5 g of 4-bromo-2-phenylthiazole (93.7 mmol), 19 g of(4-chloro-2-formylphenyl)boronic acid (103.1 mmol), 4.3 g oftetrakis(triphenylphosphine)palladium (3.7 mmol), 24.8 g of sodiumcarbonate (234 mmol), 400 mL of toluene, and 100 mL of ethanol wereintroduced into a reaction vessel, 100 mL of distilled water was addedthereto, and the mixture was then stirred for 3 hours at 120° C. Aftercompletion of the reaction, the reaction product was washed withdistilled water and extracted with ethyl acetate. The extracted organiclayer was then dried with magnesium sulfate. The solvent was removedwith a rotary evaporator, and the resulting product was purified bycolumn chromatography to obtain 20.7 g of compound 1-1 (yield: 74%).

Preparation of Compound 1-2

19.7 g of compound 1-1 (65.7 mmol), 33.8 g of (methoxymethyl)phosphoniumchloride (98.6 mmol), and 350 mL of tetrahydrofuran were introduced intoa reaction vessel, and 100 mL of 1 M potassium tert-butoxide was addeddropwise thereto at 0° C. The reaction temperature was then slowlyraised to room temperature, and the mixture was stirred for anadditional 2 hours. After completion of the reaction, the reactionproduct was extracted with ethyl acetate. The extracted organic layerwas then dried with magnesium sulfate. The solvent was removed with arotary evaporator, and the resulting product was purified by columnchromatography to obtain 16.3 g of compound 1-2 (yield: 76%).

Preparation of Compound 1-3

15.6 g of compound 1-2 (47.7 mmol) was dissolved in chlorobenzene in areaction vessel, and 1.7 mL of Eaton's reagent was slowly added dropwisethereto. The mixture was then stirred under reflux for an additional 2hours. After completion of the reaction, the reaction product was washedwith distilled water and extracted with ethyl acetate. The extractedorganic layer was then dried with magnesium sulfate. The solvent wasremoved with a rotary evaporator, and the resulting product was purifiedby column chromatography to obtain 10.5 g of compound 1-3 (yield: 71%).

Preparation of Compound 1-4

10.0 g of compound 1-3 (33.8 mmol), 10.3 g of bis(pinacholato)diborane(40.6 mmol), 1.2 g of tris(dibenzylideneacetone)dipalladium (1.4 mmol),1.1 g of 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (s-Phos) (2.8mmol), 9.9 g of potassium acetate (101.4 mmol), and 200 mL of1,4-dioxane were introduced into a reaction vessel, and the mixture wasstirred under reflux for 4 hours. After completion of the reaction, thereaction product was washed with distilled water and extracted withethyl acetate. The extracted organic layer was then dried with magnesiumsulfate. The solvent was removed with a rotary evaporator, and theresulting product was purified by column chromatography to obtain 13.1 gof compound 1-4 (yield: 100%).

Preparation of Compound C-35

13.1 g of compound 1-4 (33.8 mmol), 12 g of2-(3-bromophenyl)-4,6-diphenyl-1,3,5-triazine (30.7 mmol), 2.0 g oftetrakis(triphenylphosphine)palladium (1.7 mmol), 11.9 g of sodiumcarbonate (86 mmol), 120 mL of toluene, and 40 mL of ethanol wereintroduced into a reaction vessel, 40 mL of distilled water was addedthereto, and the mixture was then stirred for 3 hours at 120° C. Aftercompletion of the reaction, the reaction product was washed withdistilled water and extracted with ethyl acetate. The extracted organiclayer was then dried with magnesium sulfate. The solvent was removedwith a rotary evaporator, and the resulting product was purified bycolumn chromatography to obtain 20.7 g of compound C-35 (yield: 78%).

MW UV PL M.P. C-35 568.70 290 nm 427 nm 282° C.

Example 2: Preparation of Compound C-249

Preparation of Compound 2-1

30 g of compound A (134 mmol), 27 g of (5-chloro-2-formylphenyl)boronicacid (147 mmol), 6.2 g of tetrakis(triphenylphosphine)palladium (5mmol), 35.5 g of sodium carbonate (335 mmol), 270 mL of toluene, and 67mL of ethanol were introduced into a reaction vessel, 67 mL of distilledwater was added thereto, and the mixture was then stirred for 3 hours at120° C. After completion of the reaction, the reaction product waswashed with distilled water and extracted with ethyl acetate. Theextracted organic layer was then dried with magnesium sulfate. Thesolvent was removed with a rotary evaporator, and the resulting productwas purified by column chromatography to obtain 22.2 g of compound 2-1(yield: 58%).

Preparation of Compound 2-2

22.2 g of compound 2-1 (78 mmol), 40.2 g of (methoxymethyl)phosphoniumchloride (117 mmol), and 355 mL of tetrahydrofuran were introduced intoa reaction vessel, and 117 mL of 1 M potassium tert-butoxide was addeddropwise thereto at 0° C. The reaction temperature was then slowlyraised to room temperature, and the mixture was stirred for anadditional 2 hours. After completion of the reaction, the reactionproduct was extracted with ethyl acetate. The extracted organic layerwas then dried with magnesium sulfate. The solvent was removed with arotary evaporator, and the resulting product was purified by columnchromatography to obtain 10.1 g of compound 2-2 (yield: 41%).

Preparation of Compound 2-3

10 g of compound 2-2 (32 mmol) was dissolved in chlorobenzene in areaction vessel, and 1.7 mL of Eaton's reagent was slowly added dropwisethereto. The mixture was stirred under reflux for an additional 2 hours.After completion of the reaction, the reaction product was washed withdistilled water and extracted with ethyl acetate. The extracted organiclayer was then dried with magnesium sulfate. The solvent was removedwith a rotary evaporator, and the resulting product was purified bycolumn chromatography to obtain 7.4 g of compound 2-3 (yield: 82%).

Preparation of Compound 2-4

7.4 g of compound 2-3 (26 mmol), 0.9 g of s-Phos (2 mmol), 7.8 g ofpotassium acetate (79 mmol), and 156 mL of 1,4-dioxane were introducedinto a reaction vessel, and the mixture was stirred under reflux for 4hours. After completion of the reaction, the reaction product was washedwith distilled water and extracted with ethyl acetate. The extractedorganic layer was then dried with magnesium sulfate. The solvent wasremoved with a rotary evaporator, and the resulting product was purifiedby column chromatography to obtain 6.1 g of compound 2-4 (yield: 62%).

Preparation of Compound C-249

3 g of compound 2-4 (8 mmol), 2.9 g of2-(3-bromophenyl)-4,6-diphenyl-1,3,5-triazine (7 mmol), 0.4 g oftetrakis(triphenylphosphine)palladium (0.4 mmol), 2 g of sodiumcarbonate (18 mmol), 27 mL of toluene, and 9 mL of ethanol wereintroduced into a reaction vessel, 9 mL of distilled water was addedthereto, and the mixture was then stirred for 3 hours at 120° C. Aftercompletion of the reaction, the reaction product was washed withdistilled water and extracted with ethyl acetate. The extracted organiclayer was then dried with magnesium sulfate. The solvent was removedwith a rotary evaporator, and the resulting product was purified bycolumn chromatography to obtain 2.9 g of compound C-249 (yield: 71%).

MW UV PL M.P. C-249 552.64 296 nm 389 nm 276° C.

Example 3: Preparation of Compound C-258

Preparation of Compound C-258

2.6 g of compound 2-4 (7 mmol), 2.5 g of2-([1.1′-biphenyl]-4-yl)-4-[3-chlorophenyl]-6-diphenyl-1,3,5-thiazine (6mmol), 0.13 g of palladium(II) acetate (0.6 mmol), 0.5 g of s-Phos (1mmol), 5.7 g of cesium carbonate (18 mmol), 30 mL of o-xylene, and 15 mLof ethanol were introduced into a reaction vessel, 15 mL of distilledwater was added thereto, and the mixture was then stirred for 3 hours at150° C. After completion of the reaction, the reaction product waswashed with distilled water and extracted with ethyl acetate. Theextracted organic layer was then dried with magnesium sulfate. Thesolvent was removed with a rotary evaporator, and the resulting productwas purified by column chromatography to obtain 3 g of compound C-258(yield: 81%).

MW UV PL M.P. C-258 628.74 324 nm 391 nm 331° C.

Comparative Example 1: Producing a Blue Light-Emitting OLED Device notComprising an Electron Buffer Layer

An OLED device was produced as follows: A transparent electrode indiumtin oxide (ITO) thin film (10 Ω/sq) on a glass substrate for an OLED(GEOMATEC CO., LTD., Japan) was subjected to an ultrasonic washing withacetone, ethanol, and distilled water, sequentially, and then was storedin isopropanol. Next, the ITO substrate was mounted on a substrateholder of a vacuum vapor deposition apparatus.N⁴,N^(4′)-diphenyl-N⁴,N^(4′)-bis(9-phenyl-9H-carbazol-3-yl)-[1,1′-biphenyl]-4,4′-diamine(Compound HI-1) was introduced into a cell of the vacuum vapordeposition apparatus, and the pressure in the chamber of the apparatuswas then controlled to 10⁻⁷ torr. Thereafter, an electric current wasapplied to the cell to evaporate the introduced material, therebyforming a first hole injection layer having a thickness of 60 nm on theITO substrate. 1,4,5,8,9,12-hexaazatriphenylen-hexacarbonitrile (HAT-CN)(Compound HI-2) was then introduced into another cell of the vacuumvapor deposition apparatus, and an electric current was applied to thecell to evaporate the introduced material, thereby forming a second holeinjection layer having a thickness of 5 nm on the first hole injectionlayer.N-([1,1′-biphenyl]-4-yl)-9,9-dimethyl-N-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)-9H-fluorene-2-amine(Compound HT-1) was introduced into another cell of the vacuum vapordeposition apparatus. Thereafter, an electric current was applied to thecell to evaporate the introduced material, thereby forming a first holetransport layer having a thickness of 20 nm on the second hole injectionlayer.9-(naphthalen-2-yl)-3-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)-9H-carbazole(Compound HT-2) was then introduced into another cell of the vacuumvapor deposition apparatus, and an electric current was applied to thecell to evaporate the introduced material, thereby forming a second holetransport layer having a thickness of 5 nm on the first hole transportlayer. After forming the hole injection layers and the hole transportlayers, a light-emitting layer was then deposited as follows. CompoundH-1 as a host was introduced into one cell of the vacuum vapordeposition apparatus and compound F-2 as a dopant was introduced intoanother cell of the apparatus. The two materials were evaporated at adifferent rate and the dopant was deposited in a doping amount of 2 wt%, based on the total weight of the host and dopant, to form alight-emitting layer having a thickness of 20 nm on the second holetransport layer. Next,2-(3-phenanthren-9-yl)-5-(pyridin-3-yl)phenyl)-4,6-diphenyl-1,3,5-triazine(compound ETL-1) as an electron transport material was introduced intoone cell of the vacuum vapor deposition apparatus, and lithium quinolate(compound EIL-1) was introduced into another cell of the vacuum vapordeposition apparatus. The two materials were evaporated at the same rateand doped in a doping amount of 50 wt %, respectively, to form anelectron transport layer having a thickness of 35 nm on thelight-emitting layer. After depositing lithium quinolate as an electroninjection layer having a thickness of 2 nm on the electron transportlayer, an Al cathode having a thickness of 80 nm was deposited byanother vacuum vapor deposition apparatus on the electron injectionlayer. Thus, an OLED device was produced. All the materials used forproducing the OLED device were purified by vacuum sublimation at 10⁻⁶torr.

The driving voltage, luminous efficiency, and CIE color coordinates at aluminance of 1,000 nits of the produced OLED device are provided inTable 1 below.

Comparative Example 2 and Device Examples 1-1 and 1-2: Producing a BlueLight-Emitting OLED Device Comprising an Electron Buffer Layer

OLED devices were produced in the same manner as in Comparative Example1, except that the thickness of the electron transport layer was reducedto 30 nm, and an electron buffer layer having a thickness of 5 nm wasinserted between the light-emitting layer and the electron transportlayer. The driving voltage, luminous efficiency, the CIE colorcoordinates at a luminance of 1,000 nits of the OLED devices produced inComparative Example 2, and Device Examples 1-1 and 1-2 are provided inTable 1 below.

TABLE 1 Electron Volt- Luminous Color Color Buffer age EfficiencyCoordinate Coordinate Material (V) (cd/A) (x) (y) Comparative — 4.2 5.9139 87 Example 1 Comparative Com- 4.3 5.8 139 88 Example 2 pound 1Device C-35 4.1 6.5 139 87 Example 1-1 Device C-249 4.1 6.5 139 88Example 1-2

From Table 1 above, it can be seen that the OLED device comprising theorganic electroluminescent compound of the present disclosure, wherein aheteroaryl is bonded to a carbon position of a benzene ring, which isnot directly fused with an oxazole in a naphthoxazole structure, via anarylene as a linker, as an electron buffer material provides lowerdriving voltage and higher luminous efficiency, compared to the OLEDdevice comprising a conventional compound, which is different from thecompound of the present disclosure only in the position of thesubstituents, i.e., wherein a heteroaryl is bonded to a carbon positionof a benzene ring, which is directly fused with an oxazole in anaphthoxazole structure, via an arylene as a linker.

Comparative Examples 3 and 4 and Device Example 2: Producing a BlueLight-Emitting OLED Device Comprising the Compound of the PresentDisclosure as an an Electron Transport Material

OLED devices were produced in the same manner as in Comparative Example1, except that the material of the electron transport layer was changed.The driving voltage, luminous efficiency, and CIE color coordinates at aluminance of 1,000 nits of the OLED devices produced in ComparativeExamples 3 and 4, and Device Example 2 are provided in Table 2 below.

TABLE 2 Electron Volt- Luminous Color Color Transport age EfficiencyCoordinate Coordinate Material (V) (cd/A) (x) (y) Comparative ETL-2 4.35.5 141 92 Example 3 Comparative Com- 3.9 6.1 140 90 Example 4 pound 1Device C-35 4.1 6.5 140 88 Example 2

From Table 2 above, it can be seen that the OLED device comprising theorganic electroluminescent compound of the present disclosure, wherein aheteroaryl is bonded to a carbon position of a benzene ring, which isnot directly fused with an oxazole in a naphthoxazole structure, via anarylene as a linker, as an electron transport material provides superioreffects in the aspects of luminous efficiency and color coordinates,compared to the OLED device comprising a conventional compound, which isdifferent from the compound of the present disclosure only in theposition of the substituents, i.e., wherein a heteroaryl is bonded to acarbon position of a benzene ring, which is directly fused with anoxazole in a naphthoxazole structure, via an arylene as a linker.

The compounds used in the Device Examples and the Comparative Examplesare provided in Table 3 below.

TABLE 3 Hole Injection Layer/Hole Transport Layer

Light-Emitting Layer

Electron Transport Layer/Electron Buffer Layer

Electron Transport Layer/Electron Injection Layer

1. An organic electroluminescent compound represented by the followingformula 1:

wherein X₁ and X₂ each independently represent N, O, or S, with theproviso, when X₁ represents N, X₂ represents O or S, and when X₁represents O or S, X₂ represents N; Z₁ and Z₂ each independentlyrepresent hydrogen, deuterium, or -L₁-Het, with the proviso, at leastone of Z₁ and Z₂ represents -L₁-Het; R represents a substituted orunsubstituted (C6-C30)aryl, or a substituted or unsubstituted 3- to30-membered heteroaryl; R₁ to R₄ each independently represent hydrogen,deuterium, a substituted or unsubstituted (C1-C10)alkyl, a substitutedor unsubstituted (C6-C30)aryl, or a substituted or unsubstituted 3- to30-membered heteroaryl; L₁ represents a direct bond, a substituted orunsubstituted (C6-C30)arylene, or a substituted or unsubstituted 3- to30-membered heteroarylene; Het represents a substituted or unsubstituted3- to 30-membered heteroaryl; and the heteroaryl(ene) contains at leastone heteroatom selected from B, N, O, S, Si, and P.
 2. The organicelectroluminescent compound according to claim 1, wherein formula 1 isrepresented by the following formula 2 or 3:

wherein X₁, X₂, Z₁, Z₂, R, and R₁ to R₄ are as defined in claim
 1. 3.The organic electroluminescent compound according to claim 2, whereinformula 2 or 3 is represented by any one of the following formulae 4 to7:

wherein X₁, X₂, Z₁, Z₂, and R are as defined in claim
 1. 4. The organicelectroluminescent compound according to claim 1, wherein substituentsof the substituted alkyl, the substituted aryl(ene), and the substitutedheteroaryl(ene) in R, R₁ to R₄, L₁, and Het each independently are atleast one selected from the group consisting of deuterium, a halogen, acyano, a carboxyl, a nitro, a hydroxyl, a (C1-C30)alkyl, ahalo(C1-C30)alkyl, a (C2-C30)alkenyl, a (C2-C30)alkynyl, a(C1-C30)alkoxy, a (C1-C30)alkylthio, a (C3-C30)cycloalkyl, a(C3-C30)cycloalkenyl, a 3- to 7-membered heterocycloalkyl, a(C6-C30)aryloxy, a (C6-C30)arylthio, a 3- to 30-membered heteroarylunsubstituted or substituted with a (C6-C30)aryl, a (C6-C30)arylunsubstituted or substituted with a 3- to 30-membered heteroaryl, atri(C1-C30)alkylsilyl, a tri(C6-C30)arylsilyl, adi(C1-C30)alkyl(C6-C30)arylsilyl, a (C1-C30)alkyldi(C6-C30)arylsilyl, anamino, a mono- or di-(C1-C30)alkylamino, a mono- ordi-(C6-C30)arylamino, a (C1-C30)alkyl(C6-C30)arylamino, a(C1-C30)alkylcarbonyl, a (C1-C30)alkoxycarbonyl, a (C6-C30)arylcarbonyl,a di(C6-C30)arylboronyl, a di(C1-C30)alkylboronyl, a(C1-C30)alkyl(C6-C30)arylboronyl, a (C6-C30)aryl(C1-C30)alkyl, and a(C1-C30)alkyl(C6-C30)aryl.
 5. The organic electroluminescent compoundaccording to claim 1, wherein X₁ and X₂ each independently represent N,O, or S, with the proviso, when X₁ represents N, X₂ represents O or S,and when X₁ represents O or S, X₂ represents N; Z₁ and Z₂ eachindependently represent hydrogen or -L₁-Het, with the proviso, at leastone of Z₁ and Z₂ represents -L₁-Het; R represents a substituted orunsubstituted (C6-C18)aryl, or a substituted or unsubstituted 5- to18-membered heteroaryl; R₁ to R₄ each independently represent hydrogen;L₁ represents a direct bond, a substituted or unsubstituted(C6-C18)arylene, or a substituted or unsubstituted 5- to 18-memberedheteroarylene; and Het represents a substituted or unsubstituted 5- to18-membered heteroaryl.
 6. The organic electroluminescent compoundaccording to claim 1, wherein X₁ and X₂ each independently represent N,O, or S, with the proviso, when X₁ represents N, X₂ represents O or S,and when X₁ represents O or S, X₂ represents N; Z₁ and Z₂ eachindependently represent hydrogen or -L₁-Het, with the proviso, at leastone of Z₁ and Z₂ represents -L₁-Het; R represents an unsubstituted(C6-C18)aryl, or an unsubstituted 5- to 18-membered heteroaryl; R₁ to R₄each independently represent hydrogen; L₁ represents a direct bond, a(C6-C18)arylene unsubstituted or substituted with a (C1-C6)alkyl, or anunsubstituted 5- to 18-membered heteroarylene; and Het represents a 5-to 18-membered heteroaryl unsubstituted or substituted with a(C6-C12)aryl.
 7. The organic electroluminescent compound according toclaim 1, wherein Het represents a substituted or unsubstituted pyridine,a substituted or unsubstituted pyrimidine, a substituted orunsubstituted triazine, a substituted or unsubstituted quinoline, asubstituted or unsubstituted isoquinoline, a substituted orunsubstituted quinazoline, a substituted or unsubstituted quinoxaline, asubstituted or unsubstituted triazole, a substituted or unsubstitutedpyrazole, a substituted or unsubstituted benzofuran, a substituted orunsubstituted dibenzofuran, a substituted or unsubstitutedbenzothiophene, or a substituted or unsubstituted dibenzothiophene. 8.The organic electroluminescent compound according to claim 1, whereinthe compound represented by formula 1 is selected from the groupconsisting of:


9. An organic electroluminescent device comprising the organicelectroluminescent compound according to claim
 1. 10. The organicelectroluminescent device according to claim 9, wherein the organicelectroluminescent compound according to claim 1 is comprised in atleast one of an electron transport material, an electron buffermaterial, and a phosphorescent host material.